When your hair starts to go grey depends on things such as ethnic background, DNA, hormones and your environment


Question: Why does your hair turn gray?

Answer: Are you the cause of your parents’ gray hair? Many people believe that stress is one of the major causes of graying hair. As it turns out, this isn’t exactly true.

As humans age, their hair slowly turns gray and eventually turns white. By 50 years old, about 50 percent of the population has gray hair (although they might try to hide it!). A human’s chance of developing gray hair increases 10-20 percent every decade after they turn 30, although some people go gray earlier than that.

All hair starts as white hair. Before you are born, your body produces a substance called melanin that acts as a pigment to color your hair. Melanin also controls skin color. Melanin is made by special cells in your skin called melanocytes. Each strand of hair is associated with different melanocytes.

There are two types of melanin: eumelanin and phaeomelanin. Eumelanin is a dark color, while phaeomelanin is a light color. Your hair color depends on the mix of these melanins that are produced by your melanocytes. If you have light-colored hair (blonde or red), your melanocytes make more phaeomelanin. If you have darker hair (brown or black), your melanocytes produce more eumelanin. If you look at your hair closely, you might see that not all your hair strands are exactly the same color. This is because each strand has different melanocytes that might be producing different levels of the two melanins.

So why does hair turn gray? Scientists are still working on the exact reason, but it is thought that over time, melanocytes become damaged and die. When a melanocyte dies, no more melanin can be created. Each melanocyte has a supply of stem cells which are able to replace the dead melanocyte, but when that supply runs out, the melanocyte cannot be replaced, so less pigment can be created for that strand of hair. As more and more melanocytes die and cannot be replaced, hair will eventually go gray!

Hair graying happens at different rates in different people. In some, it happens quickly, while in most people it happens slowly over several decades. There are many factors that influence the age your hair starts to go gray and how fast your hair grays, including your ethnic background, the genes in your DNA, hormones and your environment. Since hair graying is mainly controlled by genetics, most people start to get gray hair at the same age as their parents did.

Next time your parents blame you for their gray hair, tell them instead that they can blame their parents!

About Ask a Scientist

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Name: Francesca Garufi

Grade: 6


Teacher: Anu Rai

Hobbies: Dance, piano, Girl Scouts

Career interest(s): Interior designer, architect  


Name: Pam Lovejoy

Title: Graduate Student in Biology, Binghamton University

Research Area: Genetics, toxicology, evolutionary biology

Interests/hobbies: Water polo, swimming, hiking 

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